Transmission crossmember bolt sizes?

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jcwren

jcwren

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I'm finally back working on my butchered '67 Barracuda. Originally a slant-6/904 car, a previous owner put a 360 and A833 trans in, but never finished the job (it's also got a GM 8.2 rearend, Dog knows why). The crossmember the PO put in is some kind of welded up hack job, and I was unable to get the shift linkages to work with it. According to Dan Brewer, I have the correct shifter and linkages for this A833. I have a crossmember from a '71 Dart's 904, and everything lines up, except the 1/2" bolts (non-original, looks like grade 2 Home Depot stuff) which worked with the hacked up crossmember don't go through one side of the factory crossmember. It looks like the bolts should be a very specific length where the body of the bolt goes through the frame, but the threads are smaller diameter where they come through the other side of the factory crossmember. I could drill it out of course, but I'd rather not.

TL;DR version -- Are crossmember bolts "special"?
 
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3/8 bolt. 3.50 inch long under head including washer. The unthreaded area is 1.75 inch.
Hope this helps

IMG_20230827_130119731_HDR.jpg

They are special, their momma told them lol
 
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MOPARMAGA said:
3/8 bolt. 3.50 inch long under head including washer. The unthreaded area is 1.75 inch.
Hope this helps

View attachment 1716134213
They are special, their momma told them lol
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Hmm, curious. The holes in one side of the crossmember are 1/2", as are the holes and bracing tubes in the frame. It's the holes in the other side of the crossmember that are a little smaller.
 
jcwren said:
Hmm, curious. The holes in one side of the crossmember are 1/2", as are the holes and bracing tubes in the frame. It's the holes in the other side of the crossmember that are a little smaller.
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67 is probably factory 1/2 inch and the 71 cross member is 3/8. You will have to either pull the cross member out and measure or just drill them out to 1/2 inch. I believe they went to 3/8 in 1970
 
I guess I'll just drill them out. It's odd that one side takes a 1/2" prefectly, and the other side is just a hair too small to pass the threads.
 
jcwren said:
I guess I'll just drill them out. It's odd that one side takes a 1/2" prefectly, and the other side is just a hair too small to pass the threads.
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Yeah that's a good idea. Yeah it is weird but even the cross member on my car takes some finesse to get correct and it was born with it.
 
The later crossmembers had a funky 3/8 bolt with a tapered 1/2 shoulder under the head. 3/8-16 x 3 3/8 long. Bolt head tapers to .490 just under the head.

P1010043.JPG
 
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66fs said:
The later crossmembers had a funky 3/8 bolt with a tapered 1/2 shoulder under the head.
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OK, that explains it then. The only reason I can imagine they did that was to make sure the bolts were inserted the correct direction. I don't know for sure which way they're supposed to go in, but the bolt heads should be closer to the rear, threads towards the engine?
 
jcwren said:
OK, that explains it then. The only reason I can imagine they did that was to make sure the bolts were inserted the correct direction. I don't know for sure which way they're supposed to go in, but the bolt heads should be closer to the rear, threads towards the engine?
Click to expand...
Sounds reasonable to me. As a design engineer, I always tried to make things only go together one way.
 
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